The present invention generally relates to controlling a work implement. More particularly, the invention relates to a unified control system for controlling the motion of a work implement such as a bucket coupled to a work vehicle such as a backhoe or an excavator.
A typical backhoe includes an elongated boom with a dipper stick assembly articulately connected to the distal end of the boom. A work implement such as a bucket, or the like, is connected to the distal end of the dipper stick assembly. The boom, the dipper stick assembly, and the work implement are relatively massive components that develop substantial inertia as they move from one position to another.
As will be appreciated by those skilled in the art, a cylinder end of each hydraulic cylinder is pivotally connected to the implement frame to allow pivotal movement of the drivers in response to movements of the backhoe apparatus to opposite sides of the implement or machine. As is conventional, each hydraulic cylinder has a piston rod that linearly extends from the cylinder end of the driver. The rod end of each cylinder is articulately connected to the swing tower as by a pin passing endwise through a weldment. The pins that connect the rod ends of the cylinders to the swing tower each extend along an axis that is parallel to the vertical swing axis of the swing tower.
The backhoe bucket is conventionally controlled by a set of operator controls. The typical operator controls provide either extension or retraction of hydraulic cylinders, or rotation of the joints connecting the backhoe members. Conventional backhoes are not configured to accept operator inputs that correspond to motions of the backhoe bucket in Cartesian space.
Traditional controls for backhoes typically only control the motions of the backhoe apparatus disregarding any constraints on the backhoe apparatus such as the avoidance of any obstacles, controlling the force applied by the backhoe apparatus, minimizing time to travel, minimizing gravity torque, preventing engine stall or backhoe tippage, or other user defined constraints. In traditional controls, such constraints are met only through the combination of skill and experience exhibited by the operator in manipulating the controls, thereby preventing operation by unskilled operators and causing erroneous operation by even skilled operators.
Many conventional backhoe controls do not control the flow of hydraulic fluid into the cylinder; rather, many conventional controls attempt to control the angular position of the backhoe apparatus joints. Also, many conventional controls do not include inertial parameters in the control design.
Conventional backhoe controls are not configured to account for the inertial parameters and forces on the backhoe members. Nor are conventional backhoe controls configured to provide hydraulic fluid flow control signals as opposed to angular rate or velocity signals. Furthermore, conventional backhoe controls are not configured to adapt to changes in available hydraulic fluid flow conditions, or changes in the linkage dynamics of the system.
Thus, there is a need and desire for a unified control for a work implement such as a bucket coupled to a work vehicle such as an excavator or a backhoe. There is also a need and desire for a unified control for a backhoe or excavator that controls the work implement tip position. There is also a need and desire for a unified control that accounts for predetermined constraints during control of the backhoe or excavator apparatus. Further still, there is a need and desire for a unified control that incorporates the positional control and constraints into the minimization of an objective criterion.
Further still, there is a need and desire for a unified control that accounts for inertial parameters and forces on the backhoe or excavator members. Further still, there is a need and desire for a unified backhoe or excavator control that provides hydraulic fluid flow control signals. Further still, there is a need and desire for a unified backhoe or excavator control that is configured to adapt to changes in available hydraulic fluid flow conditions, or changes in the linkage dynamics of the system.
The present invention relates to an apparatus for controlling a work implement. The apparatus includes a means for defining the posture of a work implement. The apparatus also includes a means for defining a unified vector, including the implement posture. Further, the apparatus includes a means for providing kinematic control signals for the implement posture. The kinematic control signal is provided by a kinematic controller configured to control a system that is any one of a redundant system, an exact system, and an overdetermined system.
The present invention also relates to a method for controlling a work implement for a work vehicle. The method includes defining the posture of the work implement. The method also includes defining a unified vector, the unified vector including a bucket posture. The method further includes defining a control objective, in terms of the unified vector. Further still, the method includes providing a kinematic control signal formulated to minimize the control objective, by applying a transformation that can be used on any one of a redundant system, an exact system, and an overdetermined system.
The present invention further relates to an apparatus for controlling a work implement for a work vehicle. The work implement includes a plurality of actuatable joints, actuatable by a plurality of hydraulic actuators. The apparatus includes a kinematic controller receiving a command signal representative of a command posture signal and a measured posture signal and providing a first output signal representative of the angular velocity of the joints of the work implement. The first output signal is generated based on the mathematical optimization of an objective criterion. The present invention still further relates to a flow controller receiving the first output signal from the kinematic controller and one of a signal representative of the actual flow and an estimated flow signal. The flow controller provides a signal representative of the stem displacement of the plurality of hydraulic actuators.
The present invention still further relates to an apparatus for controlling a work implement for a work vehicle. The work implement includes a plurality of actuatable joints, actuatable by a plurality of hydraulic actuators. The apparatus includes a kinematic controller receiving a command signal representative of a command posture signal and receiving a measured posture signal. The kinematic controller provides a first output signal representative of the angular velocity of the joints of the work implement. The first output signal is generated based on the mathematical optimization of an objective criterion. The apparatus also includes an adaptive controller for generating a cylinder force control signal.
Still further the present invention relates to a method for controlling a work implement. The work implement has n actuatable joints. The method includes defining an m-by-1 posture vector to represent bucket position and orientation with respect to a fixed Cartesian Coordinate System, defining a k-by-1 additional feature vector, and defining an objective criterion that is a function of the posture vector and the additional feature vector. The method also includes obtaining a desired n-by-1 joint angle velocity vector based on minimization of the object criterion.